1. Field of the Invention
This disclosure relates to tunable lasers, and in particular to a continuously tunable distributed bragg reflector (DBR) laser for suppressing Stimulated Brillouin Scattering.
2. Description of the Related Art
Stimulated Brillouin Scattering (SBS) typically requires artificial broadening of the linewidth of a transmitting laser at average power levels of 8-10 dBm and above, such as for non-return-to-zero (NRZ) signals. Often, artificial broadening is accomplished by direct modulation of the laser. A large linewidth enhancement factor .alpha. is desirable to minimize the associated amplitude modulation (AM), which may induce a power penalty in the receiver sensitivity. For very high launch powers the residual AM may be quite significant even when high .alpha. lasers are employed and may cause penalties of several dB's.
Tunable semiconductor lasers are known in the art for being selectively tuned to specific lasing wavelengths. S. L. Woodward et al., "A DBR Laser Tunable by Resistive Heating", IEEE PHOTONICS TECH LETTERS, Vol 4, No 12, December 1992, pp. 1330-1332, describes tuning a laser to discrete lasing wavelengths by selectively heating the passive waveguide section and/or the Bragg section of a DBR laser.
In addition, commonly assigned U.S. patent application Ser. No. 08/268,394 to Froberg et al., filed Jun. 30, 1994, entitled DATA ENCODED OPTICAL PULSE GENERATOR, describes a discretely tuned DBR laser having a current selectively applied to a resistor for selecting a temperature of the DBR laser for tuning.